1. Analysis of Jet & Rocket Propulsion Systems
P M V Subbarao
Professor
Mechanical Engineering Department
I I T Delhi
Controllable and Economic Propulsion Systems

2. Propulsion Systems

3. Jet Engine Vs Ramjet
Vac 6 3 4 5 2 1
Vjet

4. Measure of Extra Life Generation by Compressor2 3
Isentropic active compression

5. Combustion Chamber : Enhancement of Energy of would be Jet
Vac 4 3
Vjet
Define total temperature ratio across combustion chamber as
3 -- 4
s : increasing
T: increasing
p : constant???

6. Energy Balance in Combustor : 3-- 4
For unit flow rate of air thru the Jet engine:
How much fuel should be added to get a compact jet engine ?
How to achieve better fuel economy?

7. Turbine : Look for a Slave to Drive Compressor
Vac 4 5
Vjet
4 -- 5
s = constant
T : decreasing
p : decreasing

8. Sizing of Turbine : Just Enough Power4 5 T C 2 3
Duty of the Turbine is to drive the compressor : just enough power.
Enhanced vigor of Jet:

9. The Thrust Generator with better Inlet Conditions
Isentropic Expansion in a Passive Device
(Nozzle)

10. Nozzle : Steady State Stead Flow5 6
First Law for unit mass flow rate of gas:
No heat transfer and no work transfer & No Change in potential energy.

11. Performance of Turbojet Engine
Specific Thrust S
Thrust Specific Fuel Consumption TSFC

12. Performance of a Ideal Turbojet Engine : effect of Mach Number
r0p,comp = 10
0,cc=4.5 S
TSFC kg/ kN.hr
Specific Thrust kN.s/kg
TSFC
Mac

13. Parametric Cycle Analysis of Ideal Turbo Jet Engine
Selection of Safe Cruising Conditions….

14. Effect of Flight Mach Number on Fuel Economy
0,cc=4.5
r0p=1
r0p=2
r0p=3
TSFC kg/ kN.hr
r0p=5
r0p=10
r0p=20
r0p=30
Mac

15. Effect of Flight Mach Number on Compactness
0,cc=4.5
r0p=20
r0p=30
r0p=10
r0p=5
r0p=3
r0p=2
r0p=1
Specific Thrust kN.s/kg
Mac

16. Summary of Turbojet Performance
A high compressor pressure ratio is desirable for subsonic flight for good specific thrust and low fuel consumption.
A special care must be used in selecting the compressor pressure ratio for a supersonic flight.
Rapid drop in specific thrust with pressure ratio at supersonic conditions.
Rapid fall in specific thrust under supersonic conditions is still a serious concern for emergency/war use.

17. Turbo Jet with Afterburner
inlet 1 2 7 5 3 6 4

18. Comparative Study of Jet Performance with AB & w/o AB
rp = 10 & 0,cAB= 0,cc
W AB
W AB
W/O AB
TSFC
Specific Thrust
W/O AB

19. Energy Flow in Jet Engine
Energy input
Long distance travel demands high flight velocity.
A Single hot Jet was creating huge noise.
High flight velocity leads to drop in compactness and fuel economy.
A Single hot jet is blackmailing the jet engine !!!

20. An Evolved design of Turbojet
Inlet 2 3 cj
7 or hj 4 1 5 6
Total thrust may be Shared by both cold and hot jets..
In Soviet designer Arkhip Lyulka elaborated the design of turbojet and created an evolved turbojet.
Created the world's first turbofan engine, and acquired a patent for this new invention on April 22, 1941.

21. Special Design Variable for an Ideal Turbofan Engine
Inlet 2 1

22. Sizing of Fan
Inlet 2 3 1
Design Parameter : Fan Total Pressure ratio

23. Design Parameter : Compressor total pressure ratio
Sizing of Compressor
Inlet 4 2 3 1
Design Parameter : Compressor total pressure ratio

24. Sizing of Combustor 5
Inlet 4 2 3 1

25. Combined Gas Dynamic & Thermodynamic SSSF model for Turbine5
Inlet 4 2 3 6 1

26. Generation of Thrust : The Capacity
Specific Thrust based on total flow

27. Thrust Specific Fuel Consumption TSFC

28. Influence of Fan: Pressure Ratio: Mac = 0.75
r0,p,comp=15.0
a=4.0
T0max=1200K

29. Best Selling Turbofans in World CFM series

30. Current Turbofan Engines
Model
Thrust
Bypass ratio
Pressure ratio
Applications
CFM56-7B18
(86.7 kN)
5.5
32.7
Boeing
CFM56-7B20
(91.6 kN)
5.4
Boeing , Boeing
CFM56-7B22
(101 kN)
5.3
CFM56-7B24
(108 kN)
Boeing , Boeing , Boeing

31. Optimum Fan Pressure Ratio for Fuel Economy
=3 a
=4
=6
=5
r0,p,comp=24
T0max=1800K
Mac =0.9 7 12 8 10
TSFC
Fan Pressure Ratio

32. Turboprop Engine V

33. Power Generated by A Turboprop
The total propulsive power generated by an ideal turboprop is given by:

34. Pratt & Whitney PW127G Turboprop
The result is class-leading fuel consumption and low green house emissions.

35. Propulsion in Space
Sky is the Limit

36. Travel Cycle of Modern Spacecrafts

37. Basics of Rocket : generation of Thrust
Rocket takes mass stored inside combustion chamber and throws it backwards, to use the reaction force to propel the vehicle.
This is known as Rocket Propulsion
Rocket ejects mass at a given momentum rate from the nozzle and receives a thrust in the opposite direction.
Momentum rate of ejects:

38. Basic Forces Acting on A Rocket
T = Rocket thrust
D = Rocket Dynamic Drag
Vr = Velocity of rocket
mejects = Mass flow rate of ejects
mr= Mass of the rocket

39. Rocket Velocity Equation
Rocket mass X Acceleration = Thrust – Drag -gravity effect

40. Series Stage Rocket
3rd Stage
Thrusting

41. Gas Turbine Technology : Flying Machine to Ground Utilities
Self Study

42. Brayton Cycle 1-2 Isentropic compression (in a compressor)
2-3 Constant pressure heat addition
3-4 Isentropic expansion (in a turbine)
4-1 Constant pressure heat rejection

43. Analysis of Components
1 –2 : Specific work input :
2 – 3 : Specific heat input :
3 – 4 : Specific work output :
4 – 1 : Specific heat rejection :
Two Isentropic Processes sandwiched between two isobaric pressures:

44. Pressure Ratio Vs Efficiency

45. Pressure Ratio Vs Specific Work Output

46. 1872, Dr Franz Stikze’s Paradox

47. Condition for Compact Gas Turbine Power Plant

48. At maximum power:
Two Important Comments:
What if I am not interested in Compactness.
Should I prefer high Pressure Ratio for Efficient Plant?
Why the plant is compact at this condition?
What else can be inferred form this condition?

49. Condition for Economic Gas Turbine Power Plant

50. T0

51. T01 /T03
T01 /T03
T01 /T03

53. T0 s

54. GT24 (ISO 2314 : 1989) Fuel Natural gas Frequency 60 Hz
 Gross Electrical output
 187.7 MW*
 Gross Electrical efficiency
 36.9 %
 Gross Heat rate
 9251 Btu/kWh 
 Turbine speed
 3600 rpm
 Compressor pressure ratio
 32:1
 Exhaust gas flow
 445 kg/s
 Exhaust gas temperature
 612 °C
 NOx emissions (corr. to 15% O2,dry)
 < 25 vppm

55. Fuel
 Natural gas
 Frequency
 60 Hz
 Gross Electrical output
 187.7 MW*
 Gross Electrical efficiency
 36.9 %
 Gross Heat rate
 9251 Btu/kWh 
 Turbine speed
 3600 rpm
 Compressor pressure ratio
 32:1
 Exhaust gas flow
 445 kg/s
 Exhaust gas temperature
 612 °C
 NOx emissions (corr. to 15% O2,dry)
 < 25 vppm